The Shape of Polar Anisotropic Magnetizer to Reduce the Dead Zone of a Ring Bonded Magnet

A ring magnet attached under the safety window motor is used for detecting the position of the window with a hall sensor. A dead zone that the magnetic flux is weak appears between the poles of the ring bonded magnet and the larger the angle of the dead zone, the more difficult it is to detect the precise position of window. In this study, the shape of polar anisotropic magnetizer with a magnetic flux concentration structure is proposed to reduce the range of the dead zone. A magnetic equivalent circuit (MEC) was presented to provide a theoretical formula of the air gap magnetic flux density, and finite element analysis (FEA) was performed to prove the validity of the analysis. The results were analyzed through finite element analysis and the final model was selected by analyzing the inner and outer teeth thickness of the teeth of the magnetizer as design variables. The prototype of the final model was manufactured, and the validity of the analysis result was verified.